SQA a 'fail' for questioning the judgement of teachers after downgrading thousands of pupil results across the country.Rod Grant, headmaster at Clifton Hall School in Edinburgh, has demanded a full-scale independent review after almost a third of his students had their grades lowered by the education body.He blasted the exam quango and said it called into question the integrity of Scots teachers who will be called upon to help mark appeals.The new pupil grading system - brought in after